Further analysis of the association of specific B cell alloantigens and rheumatoid arthritis are projected. New antisera obtained from pregnant women and transplant patients will be utilized to confirm the initial findings. A plaque forming assay for specific antibody formation by human cells has been developed and will be studied for antibody formation in patients with various autoimmune and immune deficiency syndromes. Suppressor cells will be determined by this method. BIBLIOGRAPHIC REFERENCES: Stern, R., Fu, S.M., Fotino, M., Agnello, V. and Kunkel, H.G.: Hereditary C2 deficiency: association with skin lesions resembling the discoid lesion of systemic lupus erythematosus. Arthritis and Rheum. 19: 517, 1976. Winchester, R.J., Dupont, B., Wernet, P., Hansen, J.A., Fu, S.M., Ojea, F., Laursen, N., and Kunkel, H.G.: Recognition by pregnancy serums of several distinct non HL-A alloantigens expressed on B cells and their relationship to LD determinants. IN Leukocyte Membrane Determinants Regulating Immune Reactivity (V.P. Eijsvoogel, D. Roos, W.P. Zeijlemaker, editors) p 485 Academic Press, 1976.